J. ISSAAS Vol. 24, No. 2: 79-92 (2018) 79 COMPARATIVE STUDY OF MORPHOLOGY, MORPHOMETRICS, REPRODUCTIVE FITNESS ON CARROT DISCS AND PATHOGENICITY ON MUSA GENOTYPES OF RADOPHOLUS SIMILIS PHILIPPINE POPULATIONS Marita S. Pinili 1 , Rustico A. Zorilla †2 , Inge Van den Bergh 3 and Dirk De Waele 4,5 1 Institute of Plant Breeding 2 Institute of Weed Science, Entomology and Plant Pathology, College of Agriculture and Food Science, University of the Philippines Los Baños, College, Laguna 4031 Philippines. 3 Bioversity International, 1990 Bd de la Lironde, Parc Scientifique Agropolis II, 34397 Montpellier, France. 4 Laboratory of Tropical Crop Improvement, Department of Biosystems, Faculty of Bioscience Engineering, University of Leuven (KU Leuven), Willem de Croylaan 42, B-3001 Heverlee, Belgium. 5 Unit for Environmental Sciences and Management, North-West University, Private Bag X6001, 2520 Potchefstroom, South Africa. Corresponding author: [email protected](Received: July 2, 2018; Accepted: November 10, 2018) ABSTRACT Comparative studies were conducted on three Radopholus similis populations collected in Quezon, Laguna and Davao, Philippines from 2008 to 2010. For the first time, morphological and morphometrical characteristics of the Philippine R. similis populations were studied and showed differences for the major body regions. Consequently, reproductive fitness of the three populations on a single carrot disc at 28°C was elucidated and found different from each other. The Davao population showed high nematode density (Pf = 8,447) and reproduction ratio (Rf = 422.4) 8 weeks after inoculation (WAI) indicating greater percentage of reproductive females and found most pathogenic. Ten Musa genotypes including the resistant reference cultivars Pisang Jari Buaya and Yangambi Km5, and susceptible Grande Naine showed various degrees of response to R. similis populations. Cuarenta Dias and Latundan showed high to moderate resistance and tolerance to R. similis based on nematode counts and root damage, respectively. The most pathogenic Davao population caused significant reduction in roots weight and necrosis on the susceptible genotypes, Bungulan, Lakatan- Davao, Morado and M. balbisiana. Although nematode morphology and morphometrics failed to correlate the pathogenicity of R. similis, the reproductive fitness could help underpin selection and breeding of Musa for nematode resistance. Key words: Cuarenta Dias, Davao, Laguna, Latundan, Morado, reproduction rate INTRODUCTION The burrowing nematode Radopholus similis (Cobb) Thorne is recognized as one of the most important and widespread nematode species attacking banana and plantain ( Musa spp.). It also attacks many other crops and weeds (Davide 1992, Sarah et al. 1996, O’Bannon 1997). It is considered the main nematode problem in vast commercial plantations of Cavendish bananas (AAA) in Central and South America, and causes damage on plantains and cooking bananas in the lowlands of Central and Eastern Africa, and in the Caribbean (Sarah 2000). In the Philippines, the burrowing nematode became a serious problem in the early 1970s, when large volumes of infected Giant Cavendish planting materials from Central America were introduced for commercial production (Davide 1992). In Davao, R. similis was the most destructive nematode species of Cavendish banana followed by Helicotylenchus multicinctus and Meloidogyne spp. (Boncato and Davide 1980). Davide and
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J. ISSAAS Vol. 24, No. 2: 79-92 (2018)
79
COMPARATIVE STUDY OF MORPHOLOGY, MORPHOMETRICS,
REPRODUCTIVE FITNESS ON CARROT DISCS AND PATHOGENICITY ON
MUSA GENOTYPES OF RADOPHOLUS SIMILIS PHILIPPINE POPULATIONS
Marita S. Pinili1, Rustico A. Zorilla†2, Inge Van den Bergh3 and Dirk De Waele4,5 1Institute of Plant Breeding
2Institute of Weed Science, Entomology and Plant Pathology,
College of Agriculture and Food Science, University of the Philippines Los Baños,
College, Laguna 4031 Philippines. 3Bioversity International, 1990 Bd de la Lironde, Parc Scientifique Agropolis II,
34397 Montpellier, France. 4Laboratory of Tropical Crop Improvement, Department of Biosystems, Faculty of Bioscience
Engineering, University of Leuven (KU Leuven), Willem de Croylaan 42, B-3001 Heverlee, Belgium. 5Unit for Environmental Sciences and Management, North-West University,
Private Bag X6001, 2520 Potchefstroom, South Africa.
RResistant reference Musa genotype (Valmayor et al. 2000). SSusceptible reference Musa genotype (Valmayor et al. 2000).
Comparative study of morphology, morphometrics, reproductive fitness…..
82
The selection of these genotypes was also based on root damage assessments made during
surveys on various sites in Quezon, Oriental Mindoro, Davao and Cebu provinces, in which the
genotypes Señorita and Cardaba had the lowest percentage root necrosis (Zorilla et al. 2005). All
cultivars were maintained at the Plant Cell and Tissue Culture Laboratory in the Institute of Plant
Breeding, University of the Philippines - Los Baños.
Aggregates of plants from the proliferation medium were separated and the leaves and shoots
were excised. Plantlets were transferred in Murashige and Skoog (MS) coconut water medium for
regeneration and finally to MS rooting medium with charcoal (Murashige and Skoog 1962). At each
subculture stage of plant proliferation, an incubation condition was maintained at 28ºC with 16 h
photoperiod for 4 weeks. Acclimatized plantlets (1 week prior to planting) were transferred to plastic
pots (30 cm3 capacity) containing sterilized river sand (40%), garden soil (40%), and coir dust (20%)
and drenched with fungicide, Dithane M-45 (80% a.i. mancozeb, Dow Agro Sciences) to ensure that
the medium was nematode and fungus free. Established plants were watered as needed and fertilized
(Complete 14-14-14) every 2 weeks until inoculation. After 4 weeks, Musa genotypes were inoculated
with 1000 R. similis obtained from each population.
For the host response and nematode pathogenicity (i.e., the capacity to multiply on known
susceptible and resistant hosts and its potential damage) tests, two separate pot experiments were
conducted. Seven genotypes were used in the first batch namely: Bungulan (AAA), Cardaba (BBB),
Cuarenta Dias (AA), Lakatan-Davao (AA/AAA), Latundan (AAB) and the reference genotypes
Yangambi Km5 (AAA, resistant) (YKm5) and Grande Naine (AAA, susceptible). In the second batch,
10 genotypes were evaluated including the above mentioned cultivars, Morado (AAA), wild M.
balbisiana, and another resistant reference genotype Pisang Jari Buaya (AA) (PJB). All pot
experiments were laid out in a simple completely randomised design (CRD), with two factors
(genotypes and R. similis populations) with five replications. Uninoculated plants were included as
negative controls with the same number of replications.
Each plant was carefully uprooted and evaluated for the presence of and damage caused by
R. similis at 8 WAI. Plants were washed in running water to remove the adhering soil. Roots were
blotted dry using tissue paper or newspaper before cutting. Plant growth variables such as plant
height, girth width (measured as diam. using a caliper), shoot weight, number of functional leaves and
root weight were measured. Root damage caused by R. similis was determined following the protocol
of Speijer and De Waele (1997). Percentage of dead roots was calculated while root health was
assessed using the following scale: 1 all roots healthy, 2 most roots healthy, 3 most roots dead and 4
all roots dead. To assess root necrosis, five pieces of 10-cm root samples from each cultivar were cut
lengthwise and examined for the presence of lesions. The maximum necrosis per root half is 20%,
giving a total root necrosis ranging from 0 to 100%. Nematode density was assessed by counting the
number of eggs, juveniles, males and females. Five g of roots were macerated in a kitchen blender
three times for 10 s with 5 s intervals. The nematode suspension was sieved using a nested set of 250-,
106-, 40- and 25-µm sieves. Eggs and vermiform nematodes were collected from the 25-µm sieve.
The suspension was standardized into 50 ml aliquots. Two ml of the suspension was poured into a
counting dish for counting.
Data analysis
The homogeneity and normality of the morphometrics of R. similis populations were tested
using Levene’s and Kolmogorov-Smirnov tests, respectively. The differences in plant growth
variables between inoculated and uninoculated plants were computed and analyzed using simple t –
test and two-way ANOVA analysis, followed by Tukey’s Honestly Significant Difference (HSD) at
P<0.05 for comparisons of nematode pathogenicity. Nematode counts were log10(x+1) transformed
before analyses, while percentages dead roots and root necrosis square root transformations were
used. For normal and homogeneous populations, one-way ANOVA was used to analyze the data and
J. ISSAAS Vol. 24, No. 2: 79-92 (2018)
83
means were separated with Tukey’s HSD in comparing the effects of genotypes and nematode
populations, respectively. All paired tests used at least 0.95 combined confidence levels with
combined confidence coefficient, α = 0.5. SPSS v13.0 for Windows Software was used.
RESULTS AND DISCUSSION
Morphometrics and morphology of Radopholus similis
Female morphometrics. Differences in total female body length were observed among the
three populations. Considering the overlapping values of the total body lengths of the Quezon (611.9
µm) and Davao (625.1 µm) populations, adult females of the Laguna population were longer than the
former two populations with a total body length of 631.7 µm (Table 2). Females of the Laguna
population also had a maximum body width of 26 µm and body width at anus of 20 µm, i.e. wider
than the females of the other two populations. The stylet length of the females of each of the three
populations averaged 19.5 µm i.e. about two head-widths long with basal knobs rounded or anteriorly
pointed. The terminal lobe of the oesophagus overlapped the intestine dorsally. Gonads were paired
and outstretched, didelphic and ampidelphic with the vulval opening located near the mid-region
along the ventral side of the body. Ovaries of the three populations extended anteriorly and
posteriorly. The lengths of the posterior and anterior ovaries differed among the three populations. On
average, the length of the posterior ovary was 127.5, 153 and 124.2 µm for the Quezon, Laguna and
Davao populations, respectively. The length of the anterior ovary of the Quezon population was on
average 178.7 µm and for the Laguna and Davao populations 160 and 195 µm, respectively. Tail
lengths also differed among the different populations, being 77, 69.8 and 65 µm for the Laguna,
Davao and Quezon populations, respectively.
Table 2. Morphometrics of females of three Radopholus similis populations from the Philippines
(Quezon, Laguna and Davao; measurements in μm).
Radopholus similis population
Quezon Laguna Davao
Total body length 611.9 + 27.9
(592.2 – 631.7)
631.7 + 5.7
(632.0 – 640.0)
625.1 + 46.5
(592.2 – 658.0)
Max. body width 16.2 + 0.03
(16.2 – 16.3)
26.0 + 2.5
(22.4 – 26.0)
19.5 + 0.28
(18.7 – 19.8)
Stylet length 19.3 + 0.27
(18.7 – 19.5)
19.5 + 1.1
(18.0 – 19.5)
19.4 + 0.27
(18.7 – 19.5)
Oesphagus length 61.7 + 0.44
(60.2 – 61.7)
68.2 + 1.3
(68.2 – 70.0)
61.7 + 6.9
(52.0 – 61.7)
Tail length 65.1 + 0.1
(65.0 – 65.1)
77.0 + 0.4
(77.0 – 77.6)
69.8 + 2.3
(68.2 – 71.5)
Body width at anus 13.0 + 1.4
(12.0 – 13.8)
20.0 + 2.0
(17.2 – 20.0)
16.2 + 0.14
(16.2 – 16.4)
Head height 3.2 + 0.04
(3.2 – 3.3)
3.2 + 0.04
(3.2 – 3.3)
3.2 + 0.4
(3.2 – 3.3)
Head width 9.4 + 0.13
(9.0 – 9.4)
11.4 + 1.4
(9.4 – 11.4)
9.7 + 2.3
(6.5 – 9.7)
Anterior ovary length 178.7 + 0.68
(178.0 – 180.5)
160.0 + 0.33
(160.0 – 161.0)
195.0 + 0.23
(195.0 – 195.5)
Posterior ovary length 127.5 + 0.42
(127.0 – 128.2)
153.0 + 0.35
(152.0 – 153.5)
124.2 + 27.6
(104.7 – 143.7) Data are the average values, followed by the standard variation. The minimum and maximum values are between parentheses.
Male morphometrics. Sexual dimorphism marked all three populations. Males had spherical
heads which were smaller than that of the females head width (9.5 µm). Males also had a shorter
stylet, on average 13 µm long, with slight basal knobs, a degenerated oesophagus, and a valveless and
reduced median bulb (Table 3). On average, the total body length of the males was shorter than the
females with on average 473.8 µm (Quezon), 539.6 µm (Davao) and 596.6 µm (Laguna population)
Comparative study of morphology, morphometrics, reproductive fitness…..
84
and a maximum body width of 13 µm (Quezon), 16.2 µm (Davao) and 20 µm (Laguna population).
Based on these body measurements, males of the Laguna population were the largest. Measurements
for the tail length and body width at anus for the Laguna population also showed differences among
populations with 76.4 µm and 19.5 µm, respectively. The Davao population had 74.0 µm and 14.3 µm
tail length and body width at anus, respectively; whereas the Quezon population had the shortest tail
length with on average 52.0 µm and 17.7 µm body width at anus. Spicule and testis lengths and
gubernacula length also differed among the populations. However, no apparent differences in stylet
length and head width and height were recorded among male specimens of the three populations.
Table 3. Morphometrics of the males of three Radopholus similis populations from the Philippines
(Quezon, Laguna and Davao; measurements in μm).
Radopholus similis population
Quezon Laguna Davao
Total body length 473.8 + 1.5
(472.0 – 478.0)
596.6 + 9.3
(592.2 – 605.4)
539.6 + 7.2
(530.0 – 540.0)
Max. body width 13.1 + 0.17
(13.0 – 13.5)
20.0 + 1.1
(19.5 – 21.1)
16.2 + 0.23
(16.0 – 16.5)
Stylet length 13.0 + 0.4
(13.0 – 13.6)
13.4 + 0.36
(13.0 – 13.9)
13.0 + 0.22
(13.0 – 13.5)
Oesphagus length 62.3 + 0.42
(61.7 – 62.3)
65.0 + 1.3
(68.2 – 70.0)
64.0 + 6.9
(52.0 – 61.75)
Tail length 52.0 + 0.79
(51.0 – 53.5)
76.4 + 6.9
(71.5 – 81.25)
74.0 + 0.90
(73.5 – 74.0)
Body width at anus 17.7 + 2.4
(14.3 – 17.7)
19.5 + 0.37
(19.0 – 20.0)
14.3 + 0.21
(14.0 – 14.5)
Head height 6.5 + 0.39
(6.0 – 7.0)
6.5 + 0.30
(6.5 – 7.1)
6.5 + 0.15
(6.1 – 6.7)
Head width 9.5 + 0.0
(9.5 – 9.5)
9.5 + 0.09
(9.5 – 9.7)
9.5 + 0.06
(9.5 – 9.7)
Testis length 216.0 + 0.5
(215.0 – 216.5)
263.2 + 15.4
(131.6 – 294.8)
216.0 + 0.07
(216.0 – 216.1)
Spicule length 17.7 + 0.7
(16.7 – 17.7)
18.4 + 2.3
(16.2 – 19.4)
16.2 + 0.13
(16.0 – 16.3)
Gubernaculum 11.8 + 0.35
(11.5 – 12.0)
10.8 + 2.3
(9.7 – 13.0)
6.5 + 0.06
(6.5 – 6.6)
Data are the average values, followed by the standard variation. The minimum and maximum values are between parentheses.
Female and male morphology. Both males and females had divergent tail ends (Fig. 1). Both
tail shape and length differed within and among the three populations. Females from the Davao and
Quezon populations had pointed to tapering tails with smooth termini. By contrast, broad tails with
smooth termini were observed in 87% of the females of the Laguna population. Tails of adult females
from Davao had pointed to truncate tails with annulated to smooth termini. Sixty percent of the
females from Davao had truncated, smooth tail ends, whereas 63% of the females from Quezon had a
pointed terminus with evident annulations.
The form of the male tail ends also showed variations within and among the populations.
However, the majority of the males had a pointed to tapering tail with smooth termini. In the Davao
population, 60% of the males had broad tail ends but with annulations, while 50% of the males of the
Quezon population had truncated to pointed tails with some annulations. All males from the Laguna
population had truncated, annulated tails.
J. ISSAAS Vol. 24, No. 2: 79-92 (2018)
85
Fig. 1. Tail shapes (and their frequency of occurrence) of females and males of Radopholus similis.
In vitro reproductive fitness of Radopholus similis
All three R. similis populations completed their life cycle in 28 to 30 days. Nematode
multiplication was relatively low with a reproductive factor (Rf) ranging from 1.7 to 3 (Table 4).
These increased over time for all three populations with significant differences (P<0.05) in Rf. The
density of the Quezon population increased 1.7, 55 and 128 times at 4, 5 and 6 WAI, respectively.
However, a 50% decrease was observed for this population at 7 WAI. At 5 WAI, the densities of the
Laguna and Davao populations were statistically similar to each other but significantly (P<0.05)
lower than that of the Quezon population. The highest Rf (422.4) was observed for the Davao
population with a density of 8,447 nematodes at 8 WAI (data not shown). The population density
declined afterwards to 376 nematodes 9 WAI. The Laguna population attained its highest density of
3,577 at 7 WAI (Rf =178.9) but declined with a high number of dead nematodes observed. The
Quezon population reached its highest density (2,284) of reproductive females at 6 WAI, while the
Laguna and Davao populations reached their highest population density at 7 and 8 WAI, respectively.
The increase in reproductive females resulted in high numbers of eggs and juvenile nematodes.
Table 4. Comparative reproductive fitness of three Radopholus similis populations from the
Philippines on carrot discs at 4, 5, 6 and 7 weeks after inoculation (WAI)
Population Time
(week)1 Eggs Juveniles Males Females Pf2 Rf3 n4
Quezon
4 2 1 2 28 33 a5 1.7 a 15
5 190 174 116 628 1108 b 55.4 ab 15
6 109 70 90 2284 2553 b 127.6 b 10
7 290 55 85 679 1109 b 55.4 ab 8
Laguna
4 6 17 18 19 60 a 3.0 a 10
5 200 80 25 300 605 b 30.4 ab 10
6 780 315 80 1500 2675 c 133.8 c 10
7 830 463 213 2901 4404 c 178.9 c 9
Davao
4 4 4 8 45 61 a 3.0 a 15
5 24 60 34 483 601 a 30.1 a 13
6 112 97 126 1188 1523ab 76.2 ab 11
7 79 448 153 2452 3132 c 157.6 b 9 1Observations were made up to 10 weeks after nematode inoculation to determine the stationary phase of nematode
reproduction. However, due to high bacterial contamination of the carrot discs and an insufficient number of replicates at 8, 9 and 10 WAI for the three R. similis populations, nematode counting were done up to 7 WAI only.
2Final nematode population density (living nematodes only). 3Reproduction factor = final nematode population density/initial inoculum level (= 20). 4Number of replicates. 5Means in column per population followed by the same letter do not differ significantly according to Tukey’s HSD at P<0.05.
Data were log10(x+1) transformed prior to statistical analysis, however untransformed data are presented.
Quezon Laguna
Davao Quezon Laguna
Davao
2500x
Female
Male
20% 60% 20% 63% 37% 13% 87%
40% 60% 50% 17% 33% 100%
Comparative study of morphology, morphometrics, reproductive fitness…..
86
The growth of the three R. similis populations was plotted as a function of time (Fig. 2)
where the total nematode population density was first log10(x+1) transformed. The Quezon population
had the highest slope (1.7) compared with the other two populations (both 0.6). Due to the high
growth rate of the Quezon population, its stationary growth phase was reached at 6 WAI, which is 1
and 2 weeks earlier than the Laguna and Davao populations, respectively.
Fig. 2. Growth of three Radopholus similis populations from the Philippines as function of time
(week) after inoculation with single female per carrot disc and incubated at 28°C.
The increase in nematode population as a function of time can be described by the Gompertz
equation (Zwietering et al. 1990). The Gompertz equation; Log Pt = A + Cexp (- exp (exp [B (M-t)]),
wherein, Pt is the nematode population at incubation time t (t expressed in week), and A, B, C and M
are model parameters, is widely used for the growth of biological organisms. This model describes
three phases; (i) lag phase in which nematodes adapt to the new environment; (ii) the exponential
growth phase and; (iii) stationary growth phase due to exhaustion of nutrients. Based on the growth
curve, Quezon population had the highest slope between 4th and 5th week (exponential growth phase)
and early stationary growth phase towards 6 WAI, followed by the Laguna and Davao populations.
Pathogenicity of Radopholus similis and host response of Musa
The reduction in plant growth of selected Musa genotypes infected with the R. similis
populations observed in two separate pot experiments conducted under greenhouse conditions is
shown in Table 5. In the first experiment, Bungulan and Cardaba were severely infected by R. similis.
The percentage reductions in plant height, pseudostem girth, shoot and root weights were comparable
to cv. Grand Naine. In the cv. Latundan the percentage reduction of all measured variables were
statistically higher after inoculation with either the Laguna or Davao population compared with cv.
Cuarenta Dias and with that of Quezon R. similis – inoculated Latundan. Cuarentas Dias was the least
affected cultivar following infection with the Laguna and Davao populations with percentage
differences of -9.1 and -4.2 on plant heights, respectively. The growth parameter data of cv. Cuarenta
Dias were comparable to cv. YKm5 with less than -6.7% difference in shoot and root weights. The
reduction in root weight was evident on cvs Bungulan, Cardaba, Latundan, and Grand Naine. Root
growth of Grand Naine was poor after nematode infection which severely damaged both root and
shoots leading to lower pseudostem girth and plant height. The Davao and Laguna populations
showed significant (P<0.05) percentage reduction in plant growth on susceptible genotypes such as
Bungulan, Cardaba and Grande Naine. However, the Davao population alone significantly (P<0.05)
affected pseudostem girth, shoot and root weights with percentage reductions of -42.8, -68.5 and -
81.3, respectively. The Laguna population significantly (P<0.05) affected plant growth variables of
cv. Lakatan-Davao compared to the other two populations. The Quezon population on the other hand,
induced significant (P<0.05) reductions in all growth variables of cv. Cardaba.
0
1
2
3
4
5
0 4 5 6 7 8 9
Davao
Quezon
Laguna
Time (week)
Log
10
(Tota
l nem
ato
des
+1)
J. ISSAAS Vol. 24, No. 2: 79-92 (2018)
87
Table 5. Effect of three Radopholus similis populations from the Philippines on the growth of Musa genotypes 8 weeks after inoculation (WAI) with 1,000
nematodes per plant compared with uninoculated (UI) control plants.
Bungulan 5 24.9 28.0 A 26.3 A -0.6 A 2.1 -16.4 A -18.6 A -37.1 A 65.1 6.3 A -0.2 A -43.1 B 15.9 -34.0 A -47.2 A -73.3*B
Cardaba 5 25.8 2.2 A -3.6 A -24.3 A 2.1 3.8 A -0.8 A -25.6 A 71.4 17.1 A 1.1 A -46.4 B 17.0 -17.7 A -33.3 A -65.3*B
Cuarenta Dias 5 21.8 57.2**A 40.8*A 40.8*A 1.9 17.5 A 15.4 A 9.1 A 61.3 56.7 B 44.1 A 17.4 A 8.3 75.3 B 46.5 B 7.3A
Lakatan-Davaoa 5 25.8 24.6***A 20.2*A -11.8 B 1.9 0.6 A -0.7 A -13.2 A 69.7 -3.0 A -4.2 A -40.5 B 14.3 -51.6*A -57.3*A -78.3*A
Latundan 5 35.7 -17.5 A -55.1* B 1.5 A 1.9 -7.9 A -29.4 A -0.8 A 54.2 -4.3 A -74.3**B 26.1 A 5.1 7.5 A -70.8* B 6.7 A
Morado 5 44.9 -1.6 A -10.8*A -17.1**A 2.4 6.2 A 12.3 A -8.6 A 118.4 17.5* A 18.2 A -23.9*A 15.8 23.0 A 31.0 B 48.1*B
Musa balbisiana 5 20.1 -21.6 B 34.2 A -36.7 B 1.4 -7.9 B 48.7* B -19.6 A 32.2 -28.8 B 123.7*A -59.1 B 3.4 -39.8 A 146.6* B -71.8*B
Pisang Jari Buaya
(R)a 5 45.7 -3.1 A -17.3*A -5.3 A 3.2
-
29.4**B -20.7*A
-
26.6***AB 142.2 -34.3 A -19.3 A -32.5*A 14.9 -28.8 A 26.8 A -27.9**A
Yangambi Km 5 (R) 5 17.6 26.1 A 32.5 A 10.7 A 1.0 40.0*A 75.9***A 42.7*A 15.9 118.2*A 212.1*A 81.2 A 3.3 100.0* A 185.3**A 89.6*A
Grande Naine (S) 5 24.9 -25.7* A -28.7*A -39.8**A 2.2 -15.2 A -21.3*A -30.9*A 79.7 -22.6 A -23.8* A -47.8* B 13.0 -13.8 A -37.2 B -48.5* B
UI – means of uninoculated plants. 1Number of replicates per treatment; atreatment with four replicates in the uninoculated plants. 2Data expressed as percent mean difference = Uninoculated minus inoculated divided by uninoculated times 100, evaluated at * (P< 0.05), ** (P< 0.01) or
***(P<0.001) according to the t-test. 3Means in the same rows per parameter followed by the same letter do not differ significantly (P< 0.05) according to One-way ANOVA followed by Tukey’s HSD.
Comparative study of morphology, morphometrics, reproductive fitness…..
88
Table 6. Reproduction of three Radopholus similis populations from the Philippines and root damage on Musa genotypes 8 weeks after inoculation
(WAI) with 1,000 nematodes per plant.
Genotype n1 Nematodes/g roots2 Nematodes per root system2 Percentage dead roots3 Percentage root necrosis3
Bungulan 5 1,325 c4A5 7,638 b B 2,024 abcAB 11,124 b B 10,090 b B 3,832 abA 10.8 a A 66.5 b B 65.5 b B 42.2 b A 73.2 cAB 89.0 b B
Cardaba 5 196 abcA 289 abA 1,385 bcA 260 a A 1,448 abB 2,073 ab B 34.4 b B 6.9 abA 100 c C 49.3 b B 6.8 a A 100.0 b C
Cuarenta Dias 5 32 ab A 34 a A 61 ab A 466 a A 292 a A 1,152 ab A 3.6 a A 2.0 a A 3.1 a A 20.2 ab A 25.6 abcA 27.2 a A
Lakatan - Davao 5 228 abcA 2,068 abB 872 bc B 2,334 abA 3,095 abA 2,196 ab A 1.3 a A 51.2 b B 43.8 ab B 33.8 ab A 69.8 bcA 78.0 b A
Latundan 5 2,924 cA 4,411 b B 5,693 c B 8,912 bA 14,835 bA 23,412 b B 5.7 a B 4.0 a A 56.2 ab B 36.6 ab A 48.2 b AB 76.2 b B
Yangambi Km 5 (R) 5 8 a A 10 a A 18 a A 272 a A 339 a A 537 a A 1.2 a A 3.7 a A 3.1 a A 7.4 a A 16.0 ab A 15.6 a A
Grande Naine (S) 5 3,303 c A 2,047 abA 9,669 c B 3,780abA 7,675 b B 11,310 b B 13.7 abA 76.4 b B 100 c B 27.0 ab A 80.0 c B 100.0 b B
Pot experiment 2
Bungulan 5 275 cA 1,421 cd B 10,435 c C 3,419 cA 10,662 c B 41,983c C 4.2bcA 2.4 aA 16.1 bA 7.6 aA 24.8 aA 70.9 bcB
Cardaba 5 8 a A 1,423 cd B 2,468 bc B 69 ab A 3,158 b B 11,232b B 5.8cA 1.2 aA 21.7 bA 13.6 aA 20.2 aA 87.8 cd B
Cuarenta Dias 5 19 ab A 483 cd B 4,236 bc C 260 bcA 4,228 b B 34,692c C 0 aA 0 aA 0 aA 5.2 aA 19.2 a B 51.4 ab C
Lakatan - Davao 5 70 bcA 2,649 d B 3,794 bc B 530 bcA 4,396 b B 11,267b B 0 aA 1.5 aA 0 aA 3.8 aA 34.0 a B 51.0 abB
Latundan 5 5 a A 636 cd B 2,175 bc B 47 ab A 1,293 b B 9,712ab C 0 aA 0 aA 0 aA 4.0 aA 11.2 aA 39.0 a B
Morado 5 2 a A 104 b B 2,406 bc C 27 ab A 1,180 b B 14,273b C 0 aA 1.3 aA 2.4 abA 3.0 aA 10.1 a B 66.0abc C
Musa balbisiana 5 13 ab A 5 a A 2,056 bc B 18 a A 27 a A 2,365a B 0 aA 5.9 aA 6.3 abA 7.0 aA 12.9 aA 90.9 dB
Pisang Jari Buaya (R) 5 13 ab A 357 cdA 1,120 ab B 151ab A 7,653 bc B 3,604ab B 0 aA 0 aA 0 aA 1.9 aA 16.0 a B 55.8abc C
Yangambi Km 5 (R) 5 3 a A 6 a A 606 a B 25 a A 42 a A 2,380a B 0 aA 0 aA 0 aA 4.0 aA 9.0 aA 39.8 a B
Grande Naine (S) 5 94 bcA 232 cdA 2,709 bc B 863 cA 3,362 b B 32,425c C 1.1 abA 0 aA 0 aA 5.2 aA 13.2 aA 52.0 ab B
1Number of replicates per inoculated plants. 2Data were log (x+1) transformed prior to statistical analyses; 3Data were square root transformed prior to statistical analyses. Untransformed data are presented. 4Means in columns followed by the same small letters do not differ significantly according to One-way ANOVA followed by Tukey’s HSD at 0.05 level. 5Means in rows per parameter followed by the same capital letter do not differ significantly according to One- ANOVA followed by Tukey’s HSD at 0.05 level.
J. ISSAAS Vol. 24, No. 2: 79-92 (2018)
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In the first experiment, significant (P<0.05) differences in the susceptibility to R. similis
populations were observed. The number of nematodes per root system and per root unit on cv. YKm5
was significantly (P< 0.05) lower compared to cv. Grande Naine (Table 6). Cuarenta Dias had low
number of nematodes per root system in Quezon and Laguna populations with 466 and 292 mean
nematode counts/plant, respectively. However, in Davao population a total of 1,152 nematodes were
recovered per plant. On the other hand, Bungulan and Latundan were statistically (P<0.05) as
susceptible as Grande Naine to R. similis. The highest nematode count per root system and per root
unit was recovered from Latundan with 5,693 and 23,412 nematodes, respectively. The number was
significantly (P<0.05) higher compared with all genotypes. Significant (P<0.05) differences on
percentage dead roots and percentage root necrosis were observed from Bungulan, Cardaba,
Latundan, Lakatan-Davao and Grande Naine. The abovementioned cultivars also had root health
ratings of 3 to 4 however data on RH are not shown. Using Davao population Cuarenta Dias and
YKm5 showed most healthy roots (RH = 2) and lowest percentage root necrosis of 27.2 and 15.6,
respectively.
In the second experiment Latundan was significantly (P<0.05) affected in terms of plant
growth and root damage variables. Plant height, shoot weight and roots weight showed percentage
differences of -55.1, -74.8 and -70.8, respectively, when inoculated with the Laguna population.
These data in reference to the uninoculated control were higher than the percentage difference of the
susceptible check. Plant height of Morado also showed significant (P<0.05) percentage reduction,
however the level was far lower than Latundan. Lakatan-Davao on the other hand had
significantly(P<0.05) higher percentage reductions on root weight with -51.6, -57.3 and -78.3 when
inoculated with Quezon, Laguna and Davao populations, respectively. Bungulan and Cardaba which
had the highest percentage reductions during the first evaluation, only showed significant (P<0.05)
reductions on root weight when inoculated with Davao population. Wild M. balbisiana (98-617) had
significant (P<0.05) reduction on root weight (-71.8%) when inoculated with the Davao population.
However, M. balbisiana did not exihibit significant reductions on plant height, pseudostem girth, and
shoot weight. The reference genotype YKm5 once again showed resistant reaction against R. similis